CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 382,493	$ 346,950
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of energy-related products and services business		(10,404)
Depreciation and amortization including nuclear fuel	360,570	370,107
Deferred fuel and purchased power	51,533	30,965
Deferred fuel and purchased power amortization	(91,894)	(121,018)
Allowance for equity funds used during construction	(15,639)	(18,697)
Deferred income taxes	206,501	131,582
Change in derivative instruments fair value	(943)	1,861
Changes in current assets and liabilities:
Customer and other receivables	(76,697)	(47,410)
Accrued unbilled revenues	(11,186)	(80,877)
Materials, supplies and fossil fuel	(23,873)	(25,532)
Other current assets	(10,035)	(1,581)
Accounts payable	(69,776)	29,340
Accrued taxes and income tax receivable - net	76,365	89,534
Other current liabilities	17,071	30,300
Change in margin and collateral accounts - assets	1,980	33,591
Change in margin and collateral accounts - liabilities	114,579	85,785
Change in unrecognized tax benefits	(3,554)	12,123
Change in other long-term assets	(15,205)	(10,678)
Change in other long-term liabilities	37,181	74,565
Net cash flow provided by operating activities	929,471	920,506
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(670,684)	(643,261)
Contributions in aid of construction	41,451	36,351
Allowance for borrowed funds used during construction	(10,428)	(14,371)
Proceeds from sale of energy-related products and services business		45,111
Proceeds from nuclear decommissioning trust sales	295,126	405,637
Investment in nuclear decommissioning trust	(308,063)	(417,957)
Proceeds from sale of life insurance policies		55,444
Other	(520)	(1,246)
Net cash flow used for investing activities	(653,118)	(534,292)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	351,081	470,353
Repayment of long-term debt	(421,703)	(228,457)
Short-term borrowings and payments - net		(16,600)
Dividends paid on common stock	(167,074)	(166,197)
Common stock equity issuance	9,684	14,953
Distributions to noncontrolling interests	(2,630)	(2,610)
Other	185	(3,132)
Net cash flow provided by (used for) financing activities	(230,457)	68,310
NET INCREASE IN CASH AND CASH EQUIVALENTS	45,896	454,524
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	33,583	110,188
CASH AND CASH EQUIVALENTS AT END OF PERIOD	79,479	564,712
Cash paid during the period for:
Income taxes, net of (refunds)	(651)	5,676
Interest, net of amounts capitalized	$ 152,582	$ 163,250